1. Field of the Invention
The present invention relates to a molded protective strip for automobiles. More particularly, the present invention relates to a molded protective strip for automobiles which can be prepared without using a vinyl chloride resin, shows almost no heat shrinkage, has a small coefficient of linear expansion, is excellent in dimensional stability, and exhibits excellent appearance as an exterior part of automobiles.
2. Description of the Related Arts
Heretofore, side protective strips for automobiles have been produced mainly by using vinyl chloride resins. However, vinyl chloride resins have a drawback in that toxic gases are generated when they are burnt for disposal. Number of type of resin used in automobiles are being reduced to promote recycling of resins. Vinyl chloride resins are progressively being replaced by polypropylene resins because of these reasons. However, polypropylene resins have a drawback in that the resins have large coefficients of linear expansion because of their crystallizing nature, and show large dimensional changes when long molded articles such as protective strips are prepared by using them. Recently, the gas injection molding process (referred to as GIM, hereinafter) is used for molding various products for the purpose of simultaneously keeping strength and decreasing weight of the molded products [for example, "Nikkei Materials and Technology", Volume 135, Page 44 (1993)]. In GIM, a cavity is formed at the inside of the molded product by injecting a gas into the mold during the injection molding. This process has enabled designs of uneven thickness and hollow structures which are impossible by the conventional injection molding. Therefore, this process has the advantage of achieving simultaneous reduction in weight and cost.
In spite of the advantage described above, it is the real situation that no attempt has been made to increase accuracy of long molded articles, such as protective strips for automobiles, by using GIM.